Of the four hosts whose results do not match, two have a history of invalid results, i.e., they're producing bad calculations (excessive overclocking, bad memory, etc.) A third host has no invalid tasks, but does have a second inconclusive task, so it's probably having problems too.
So of the four computers, two are almost certainly faulty, a third is likely to be faulty, and one computer is probably working correctly. Just coincidence that they all worked on the same task.
My lucky number is 75898524288+1